Magnetic materials with high curie temperatures and dielectric constants

ABSTRACT

Disclosed herein are ceramic materials, such as bismuth substituted garnets, which can have high curie temperatures and high dielectric constants. In certain implementations, indium can be incorporated into the ceramic to improve certain properties and to avoid calcium compensation. The ceramic materials disclosed herein can be particular advantageous for below resonance applications.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application claims priority to U.S. App. No. 62/699,857, filed Jul.18, 2018, the entirety of which is incorporated by reference herein.

BACKGROUND Field

The present disclosure generally relates to garnets having advantageousproperties for below resonance applications, such as high curietemperatures and high dielectric constants.

Description of the Related Art

Various crystalline materials with magnetic properties have been used ascomponents in electronic devices such as cellular phones, biomedicaldevices, and RFID sensors. Garnets are crystalline materials withferrimagnetic properties particularly useful in RF electronics operatingin the lower frequency portions of the microwave region. Many microwavemagnetic materials are derivatives of Yttrium Iron Garnet (YIG), asynthetic form of garnet widely used in various telecommunicationdevices largely because of its favorable magnetic properties such asnarrow linewidth at its ferromagnetic resonance frequency. YIG isgenerally composed of yttrium, iron, and oxygen, and is possibly dopedwith one or more other rare earth metals such as lanthanides orscandium.

SUMMARY

Disclosed herein are embodiments of a ceramic material with lowtemperature sensitivity, the ceramic material having a composition ofY_(1−x−2y)Bi_(x)Ca_(2y)Fe_(1−z−y)In_(z)V_(y)O₁₂ and having a dielectricconstant of at least 25. In some embodiments, the dielectric constantcan be at least 30.

Also disclosed herein are embodiments of a ceramic material with lowtemperature sensitivity, the ceramic material having a composition of (Yor Gd)_(1−x−2y)Bi_(x)Ca_(2y)Fe_(1−z−y)In_(z)V_(y)O₁₂ and having adielectric constant of at least 25. In some embodiments, the dielectricconstant can be at least 30.

In some embodiments, the ceramic material does not include aluminum. Insome embodiments, in 0<x<1.75, 0<y<0.8, and 0<z<0.7. In someembodiments, 1.4<x<1.6, 0<y<0.8, and 0.2<z<0.7. In some embodiments, theceramic material has a Curie temperature of at least 210. In someembodiments, the ceramic material has a Curie temperature of at least220. In some embodiments, the ceramic material has a magnetization of atleast 1000. In some embodiments, the ceramic material has amagnetization of at least 1200.

In some embodiments, the ceramic material has a composition including:Bi_(1.4)Y_(0.66)Ca_(0.94)In_(0.4)V_(0.47)Fe_(4.13)O₁₂;Bi_(1.4)Y_(0.62)Ca_(0.98)In_(0.4)V_(0.49)Fe_(4.11)O₁₂;Bi_(1.4)Y_(0.58)Ca_(1.02)In_(0.4)V_(0.51)Fe_(4.09)O₁₂;Bi_(1.4)Y_(0.54)Ca_(1.06)In_(0.4)V_(0.53)Fe_(4.07)O₁₂;Bi_(1.4)Y_(0.50)Ca_(1.11)In_(0.4)V_(0.55)Fe_(4.05)O₁₂;Bi_(1.4)Y_(0.46)Ca_(1.14)In_(0.4)V_(0.57)Fe_(4.03)O₁₂;Bi_(1.4)Y_(0.42)Ca_(1.18)In_(0.4)V_(0.59)Fe_(4.01)O₁₂;Bi_(1.4)Y_(0.38)Ca_(1.22)In_(0.4)V_(0.61)Fe_(3.99)O₁₂; orBi_(1.4)Y_(0.34)Ca_(1.26)In_(0.4)V_(0.63)Fe_(3.97)O₁₂.

Further disclosed herein are embodiments of a ceramic material with lowtemperature sensitivity, the ceramic material having a composition ofY_(1−x−2y)Bi_(x)Ca_(2y+a)Fe_(1−z−y a)In_(z)V_(y)Zr_(a)O₁₂ and having adielectric constant of at least 30.

Further disclosed herein are embodiments of a ceramic material with lowtemperature sensitivity, the ceramic material having a composition of (Yor Gd)_(1−x−2y)Bi_(x)Ca_(2y+a)Fe_(1−z−y−a)In_(z)V_(y)Zr_(a)O₁₂ andhaving a dielectric constant of at least 30.

In some embodiments, the ceramic material does not include aluminum. Insome embodiments, wherein 0<x<1.75, 0<y<0.8, and 0<z<0.7. In someembodiments, 1.4<x<1.6, 0<y<0.8, and 0.2<z<0.7. In some embodiments, theceramic material has a Curie temperature of at least 210. In someembodiments, the ceramic material has a Curie temperature of at least220. In some embodiments, the ceramic material has a magnetization of atleast 1000. In some embodiments, the ceramic material has amagnetization of at least 1200.

Also disclosed herein are embodiments of an isolator including theceramic material discussed herein.

Also disclosed herein are embodiments of a method of forming a syntheticgarnet having temperature insensitivity, the method comprisingincorporating bismuth, calcium, indium, and vanadium into a crystalstructure of a yttrium iron garnet structure to achieve the compositionY_(1−x−2y)Bi_(x)Ca_(2y)Fe_(1−z−y)In_(z)V_(y)O₁₂ having a dielectricconstant of at least 30.

Also disclosed herein are embodiments of a method of forming a syntheticgarnet having temperature insensitivity, the method comprisingincorporating bismuth, calcium, indium, and vanadium into a crystalstructure of a yttrium iron garnet structure to achieve the composition(Y, Gd)_(1−x−2y)Bi_(x)Ca_(2y)Fe_(1−z−y)In_(z)V_(y)O₁₂ having adielectric constant of at least 30.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows how materials having one or more featuresdescribed herein can be designed, fabricated, and used.

FIG. 2 depicts an yttrium based garnet crystal lattice structure.

FIG. 3 illustrates shows the effect of the Curie temperature on amaterial.

FIG. 4 illustrates an example process flow for making an embodiment of amodified synthetic garnet having one or more features described herein.

FIG. 5 shows an example ferrite device having one or more garnetfeatures as described herein.

FIGS. 6A and 6B show examples of size reduction that can be implementedfor ferrite devices having one or more features as described herein.

FIGS. 7A and 7B show an example circulator/isolator having ferritedevices as described herein.

FIG. 8 shows an example of a packaged circulator module.

FIG. 9 shows an example RF system where one or more ofcirculator/isolator devices as described herein can be implemented.

FIG. 10 shows a process that can be implemented to fabricate a ceramicmaterial having one or more features as described herein.

FIG. 11 shows a process that can be implemented to form a shaped objectfrom powder material described herein.

FIG. 12 shows examples of various stages of the process of FIG. 11.

FIG. 13 shows a process that can be implemented to sinter formed objectssuch as those formed in the example of FIGS. 11 and 12.

FIG. 14 shows examples of various stages of the process of FIG. 13.

FIG. 15 illustrates a perspective view of a cellular antenna basestation incorporating embodiments of the disclosure.

FIG. 16 illustrates housing components of a base station incorporatingembodiments of the disclosed material.

FIG. 17 illustrates a cavity filter used in a base station incorporatingembodiments of the material disclosed herein.

FIG. 18 illustrates an embodiment of a circuit board includingembodiments of the material disclosed herein.

DETAILED DESCRIPTION

Disclosed herein are embodiments of synthetic garnets, such astemperature-insensitive synthetic garnets, and methods of manufacturingthem. In particular, an excess amount of bismuth atoms can beincorporated into the garnet lattice structure in order to increase theoverall dielectric constant of the material without experiencingdeleterious effects to other magnetic or electrical aspects of thegarnet. For example, bismuth substituted ferromagnetic garnets may showenhanced dielectric constants as a sintered ceramic, making them usefulfor miniaturizing isolators and circulators in commercial wirelessinfrastructure devices and base stations. Embodiments of the disclosedmaterials can be advantageously used in isolators and circulators, inparticular for below resonance applications. Embodiments of thedisclosed materials can have a high dielectric constant and high Curietemperature while limiting magnetization.

Previous solutions have involved the doping of the bismuth-based garnetswith large amounts of aluminum, typically to modify the saturationmagnetization. However, the incorporation of aluminum tends to depressthe Curie temperatures of the materials, thus limiting the temperaturerange use. Accordingly, embodiments of the disclosed materials can begenerally aluminum free (e.g., can contain no aluminum, can containabout 0% aluminum, or can contain only trace amounts of aluminum). Thiscan allow the materials to have high Curie temperatures, making themmore temperature insensitive, while also having high dielectricconstants.

FIG. 1 schematically shows how one or more chemical elements (block 1),chemical compounds (block 2), chemical substances (block 3) and/orchemical mixtures (block 4) can be processed to yield one or morematerials (block 5) having one or more features described herein. Insome embodiments, such materials can be formed into ceramic materials(block 6) configured to include a desirable dielectric property (block7), a magnetic property (block 8) and/or an advanced material property(block 9).

In some embodiments, a material having one or more of the foregoingproperties can be implemented in applications (block 10) such asradio-frequency (RF) application. Such applications can includeimplementations of one or more features as described herein in devices12. In some applications, such devices can further be implemented inproducts 11. Examples of such devices and/or products are describedherein.

Synthetic Garnets

Disclosed herein are methods of modifying synthetic garnet compositions,such as Yttrium Iron Garnet (YIG) or Gadolinium Iron Garnet (GIG), toincrease the dielectric constant of the material. However, it will beunderstood that other synthetic garnets, such as yttrium aluminum garnetor gadolinium gallium garnet, can be used as well. Also disclosed hereinare synthetic garnet materials having high dielectric constant, methodsof producing the materials, and the devices and systems incorporatingsuch materials.

Synthetic garnets typically have the formula unit of A₃B₅O₁₂, where Aand B are trivalent metal ions. Yttrium Iron Garnet (YIG) is a syntheticgarnet having the formula unit of Y₃Fe₅O₁₂, which includes Yttrium (Y)in the 3+ oxidation state and Iron (Fe) in the 3+ oxidation state. Thecrystal structure of a YIG formula unit is depicted in FIG. 2. As shownin FIG. 2, YIG has a dodecahedral site, an octahedral site, and atetrahedral site. The Y ions occupy the dodecahedral site while the Feions occupy the octahedral and tetrahedral sites. Each YIG unit cell,which is cubic in crystal classifications, has eight of these formulaunits.

The modified synthetic garnet compositions, in some embodiments,comprise substituting some or all of the Yttrium (Y) in Yttrium IronGarnets (YIG) with a combination of other ions such that the resultingmaterial maintains desirable magnetic properties for microwaveapplications, for example high dielectric constants. There have beenpast attempts toward doping YIG with different ions to modify thematerial properties. Some of these attempts, such as Bismuth (Bi) dopedYIG, are described in “Microwave Materials for Wireless Applications” byD. B. Cruickshank, which is hereby incorporated by reference in itsentirety. However, in practice ions used as substitutes may not behavepredictably because of, for example, spin canting induced by themagnetic ion itself or by the effect of non-magnetic ions on theenvironment adjacent magnetic ions, reducing the degree alignment. Thus,the resulting magnetic properties cannot be predicted. Additionally, theamount of substitution is limited in some cases. Beyond a certain limit,the ion will not enter its preferred lattice site and either remains onthe outside in a second phase compound or leaks into another site.Additionally, ion size and crystallographic orientation preferences maycompete at high substitution levels, or substituting ions are influencedby the ion size and coordination of ions on other sites. As such, theassumption that the net magnetic behavior is the sum of independentsub-lattices or single ion anisotropy may not always apply in predictingmagnetic properties.

Considerations in selecting an effective substitution of rare earthmetals in YIG for microwave magnetic applications include theoptimization of the density, the magnetic resonance linewidth, thesaturation magnetization, the Curie temperature, the dielectric constantof the material, and the dielectric loss tangent in the resultingmodified crystal structure. Magnetic resonance is derived from spinningelectrons, which when excited by an appropriate radio frequency (RF)will show resonance proportional to an applied magnetic field and thefrequency. The width of the resonance peak is usually defined at thehalf power points and is referred to as the magnetic resonancelinewidth. It is generally advantageous for the material to have a lowlinewidth because low linewidth manifests itself as low magnetic loss,which is required for all low insertion loss ferrite devices. Themodified garnet compositions according to preferred embodiments of thepresent invention provide single crystal or polycrystalline materialswith reduced Yttrium content and yet maintaining low linewidth and otherdesirable properties for microwave magnetic applications.

In some embodiments, a Yttrium based garnet is modified by substitutingBismuth (Bi³⁺) for some of the Yttrium (Y³⁺) on the dodecahedral sitesof the garnet structure in combination with introducing one or moreions, such as divalent (+2), trivalent (+3), tetravalent (+4),pentavalent (+5) or hexavalent (+6) non-magnetic ions to the octahedralsites of the structure to replace at least some of the Iron (Fe³⁺). Insome embodiments, one or more high valency non-magnetic ions such asZirconium (Zr⁴⁺) or Niobium (Nb⁵⁺) can be introduced to the octahedralsites. Similar approaches can be taken for Gadolinium based garnets.

In some embodiments, a Yttrium based garnet is modified by introducingone or more high valency ions with an oxidation state greater than 3+ tothe octahedral or tetrahedral sites of the garnet structure incombination with substituting Calcium (Ca²⁺) for Yttrium (Y³⁺) in thedodecahedral site of the structure for charge compensation induced bythe high valency ions, hence reducing the Y³⁺ content. Whennon-trivalent ions are introduced, valency balance is maintained byintroducing, for example, divalent Calcium (Ca²⁺) to balance thenon-trivalent ions. For example, for each 4+ ion introduced to theoctahedral or tetrahedral sites, one Y³⁺ ion can be substituted with aCa²⁺ ion. For each 5+ ion, two Y³⁺ ions can be replaced by Ca²⁺ ions.For each 6+ ion, three Y³⁺ ions can be replaced by Ca²⁺ ions. For each6+ ion, three Y³⁺ ions can be replaced by Ca²⁺ ions. In one embodiment,one or more high valence ions selected from the group consisting ofZr⁴⁺, Sn⁴⁺, Ti⁴⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, W⁶⁺, and Mo⁶⁺ is introduced to theoctahedral or tetrahedral sites, and divalent Calcium (Ca²⁺) is used tobalance the charges, which in turn reduces Y³⁺ content. Similarapproaches can be taken for Gadolinium based garnets.

In some embodiments, a Yttrium based garnet is modified by introducingone or more high valency ions, such as Vanadium (V⁵⁺), to thetetrahedral site of the garnet structure to substitute for Fe³⁺ tofurther reduce the magnetic resonance linewidth of the resultingmaterial. Without being bound by any theory, it is believed that themechanism of ion substitution causes reduced magnetization of thetetrahedral site of the lattice, which results in higher netmagnetization of the garnet, and by changing the magnetocrystallineenvironment of the ferric ions also reduces anisotropy and hence theferromagnetic linewidth of the material. Similar approaches can be takenfor Gadolinium based garnets.

In some embodiments, a combination of high Bismuth (Bi) doping combinedwith Vanadium (V) and/or Zirconium (Zr) induced Calcium (Ca) valencycompensation could effectively displace all or most of the Yttrium (Y)in microwave device garnets. Further, certain other high valency ionscould also be used on the tetrahedral of octahedral sites and that afairly high level of octahedral substitution in the garnet structure ispreferred in order to obtain minimized magnetic resonance linewidth.Moreover, Yttrium displacement can be accomplished by adding Calcium inaddition to Bismuth to the dodecahedral site. Doping the octahedral ortetrahedral sites with higher valency ions, preferably greater than 3+,could allow more Calcium to be introduced to the dodecahedral site tocompensate for the charges, which in turn would result in furtherreduction of Yttrium content. Similar approaches can be taken forGadolinium based garnets.

Modified Synthetic Garnet Compositions

Disclosed herein are embodiments of synthetic garnets that can have acombination of advantageous properties which can make the materialparticularly useful for radiofrequency applications, such asbelow-resonance applications. Specifically, embodiments of the disclosedgarnet can have low magnetization while also having high dielectricconstants and/or high Curie temperatures. These properties can allow thesynthetic garnets to be generally “temperature insensitive” or“temperature stable”, meaning that the properties do not drasticallychange with changes in temperature. Accordingly, embodiments of thedisclosure can be advantageous in environments in which they wouldexperience temperature flux, such as caused by heating/cooling of thematerial during operation. Further, embodiments of the disclosure can beadvantageously used for circulator and isolators for radiofrequencydevices.

In particular, embodiments of the disclosure can have dielectricconstants above 20 (or above about 20) with saturation magnetizationsbelow 1200 (or below about 1200), which can be advantageous for belowresonance isolator and circulator applications. In particular,embodiments of the material are particularly useful in the bands above 1GHz (or above about 1 GHz), though they could be used at higherfrequency as well, which are subject to carrier aggregation, and can berelated to magnetization (4PiMs) by the gyromagnetic ratio,approximately 2.8 MHz per Gauss of magnetization. Carrier aggregation isthe grouping of individual segments of spectra into one continuous band.In some embodiments, the material can be used at frequencies up to 6 GHz(or up to about 6 GHz). As a result, each carrier, rather than havingstrips of bandwidth distributed throughout the range of allowed spectra,have only one wider band to operate in.

In some embodiments, increased amounts of bismuth, along with balancingcharges from other elements, can be added into the crystal structure inorder to improve the magnetoelectric properties of the garnet while notreducing other magnetoelectric properties.

In some embodiments, the modified synthetic garnet composition can bedefined by a general composition:Y_(1−x−2y)Bi_(x)Ca_(2y)Fe_(1−z−y)In_(z)V_(y)O₁₂ In some embodiments,0<x<1.75. In some embodiments, 1.4<x<1.6. In some embodiments, 0<y<0.8.In some embodiments, 0<z<0.7. In some embodiments, 0.2<z<0.7. Thecalcium can be used to compensate for any vanadium added into thestructure. In some embodiments, zirconium (Zr) can be used instead ofindium (In).

In some embodiments, the modified synthetic garnet composition can bedefined by a general composition: (Y,Gd)_(1−x−2y)Bi_(x)Ca_(2y)Fe_(1−z−y)In_(z)V_(y)O₁₂ In some embodiments,0<x<1.75. In some embodiments, 1.4<x<1.6. In some embodiments, 0<y<0.8.In some embodiments, 0<z<0.7. In some embodiments, 0.2<z<0.7. Thecalcium can be used to compensate for any vanadium added into thestructure. Due to variations in the crystal structure through the use ofGd, the O content may be approximately or about 12, such as 11.97. Insome embodiments, zirconium (Zr) can be used instead of indium (In).

In some embodiments, the modified synthetic garnet composition can bedefined by a general composition:Y_(1−x−2y)Bi_(x)Ca_(2y+a)Fe_(1−z−y−a)In_(z)V_(y)Zr_(a)O₁₂ In someembodiments, 0<x<1.75. In some embodiments, 1.4<x<1.6. In someembodiments, 0<x<1.6. In some embodiments, 0<y<0.8. In some embodiments,0<z+a<0.7. In some embodiments, 0.2<z+a<0.7. In some embodiments,0<z<0.7. In some embodiments, 0.2<z<0.7. In some embodiments, 0<a<0.7.In some embodiments, 0.2<a<0.7. In some embodiments, zirconium (Zr) canbe used instead of indium (In).

In some embodiments, the modified synthetic garnet composition can bedefined by a general composition: (Y orGd)_(1−x−2y)Bi_(x)Ca_(2y+a)Fe_(1−z−y−a)In_(z)V_(y)Zr_(a)O₁₂ In someembodiments, 0<x<1.75. In some embodiments, 1.4<x<1.6. In someembodiments, 0<x<1.6. In some embodiments, 0<y<0.8. In some embodiments,0<z+a<0.7. In some embodiments, 0.2<z+a<0.7. In some embodiments,0<z<0.7. In some embodiments, 0.2<z<0.7. In some embodiments, 0<a<0.7.In some embodiments, 0.2<a<0.7. Due to variations in the crystalstructure through the use of Gd, the O content may be approximately orabout 12, such as 11.97. In some embodiments, zirconium (Zr) can be usedinstead of indium (In).

In some embodiments, about 1.4 formula units of bismuth (Bi) can besubstituted for some of the yttrium (Y) and/or gadolinium (Gd) on thedodecahedral site. In some embodiments, greater than about 1.4 formulaunits of bismuth (Bi) can be substituted for some of the yttrium (Y)and/or gadolinium (Gd) on the dodecahedral site. In some embodiments,between about 1.8 and about 2.0 formula units of bismuth (Bi) and/orgadolinium (Gd) can be substituted for some of the yttrium (Y) on thedodecahedral site. In some embodiments, between about 1.4 and about 2.5formula units of bismuth (Bi) can be substituted for some of the yttrium(Y) and/or gadolinium (Gd) on the dodecahedral site. In someembodiments, up to 3.0 formula units of bismuth (Bi) can be substitutedfor some of the yttrium (Y) and/or gadolinium (Gd) on the dodecahedralsite. The high levels of bismuth, which can results in advantageousproperties, can be achieved through certain atom inclusions and methodsof manufacturing, as discussed below.

In some embodiments, indium (In) can be incorporated into the material,for example for Fe or Zr on an octahedral site of the garnet. This canallow for the avoidance of zirconium (Zr), which may require chargebalancing by calcium (Ca), as In has a formal charge of +3. Thus, insome embodiments the material may contain no, or only trace amounts, ofzirconium. Further, the inclusion of indium does not require chargebalancing for compensation. As a result, vanadium may be used to varythe magnetization. The adjustment in the calcium and vanadium contenthas a less detrimental effect on the Curie temperature than zirconiumdoped materials. Vanadium is unique among non-magnetic ions in beingable to substitute for Fe with minimal degradation in the Curietemperature. However, in other embodiments Fe and/or Zr can remain.

The inclusion can reduce the magnetocrystalline anisotropy energy,thereby improving 3 dB linewidth. Since In, unlike Zr, does not requireCa as a compensating ion, it allows for the substitution of more V intothe tetrahedral site allowing for lower magnetization values to beachieved.

In many previous solutions of the art, a large amount of aluminum istypically incorporated into the garnet to modify the saturationmagnetization. However, aluminum can depress the Curie temperature ofmagnetic materials, such as the synthetic garnet, which significantlylimits the temperature range of use.

Accordingly, embodiments of the disclosure can be aluminum free (e.g.,contain no (or trace amounts of) aluminum). In some embodiments, thecomposition can contain 0 wt. % aluminum (or about 0 wt. % aluminum). Insome embodiments, the composition can contain less than 1, 0.5, 0.1,0.05, or 0.01 (or less than about 1, about 0.5, about 0.1, about 0.05,or about 0.01) wt. % aluminum. Further, aluminum oxide may not be usedin the manufacturing of the material. Typically, aluminum oxide is usedas a non-magnetic ion to substitute on the tetrahedral site for Fe andreduce the saturation magnetization of the material. However, it canhave the undesirable effect of reducing the Curie temperature. This canallow the synthetic garnets to have high Curie temperatures, as well asthe other properties discussed above. In particular, the use of indiumand combinations of zirconium and vanadium can produce low magnetizationmaterials with high dielectric constants and Curie temperatures. Thus,embodiments of the disclosure can have improved temperature stability.In some embodiments, the material can be indium free and aluminum free.

Table 1 illustrates example compositional formulas as well as theirachieved properties.

TABLE 1 Example Synthetic Garnets and Properties Density 3 dB LinewidthMagnetization Curie Temp. Dielectric Formula (g/cm³) (Oe) (4πM) (° C.)Constant Bi_(1.4)Y_(.66)Ca_(.94)In_(.4)V_(.47)Fe_(4.13)O₁₂ 5.85 68 1263221.87 Bi_(1.4)Y_(.62)Ca_(.98)In_(.4)V.₄₉Fe_(4.11)O₁₂ 5.831 70 1231219.78 Bi_(1.4)Y_(.58)Ca_(1.02)In_(.4)V_(.51)Fe_(4.09)O₁₂ 5.818 67 1214217.78 Bi_(1.4)Y_(.54)Ca_(1.06)In_(.4)V_(.53)Fe_(4.07)O₁₂ 5.799 67 1175217.88 Bi_(1.4)Y_(.50)Ca1_(.11)In_(.4)V_(.55)Fe_(4.05)O₁₂ 5.779 64 1148218.27 Bi_(1.4)Y_(.46)Ca_(1.14)In_(.4)V_(.57)Fe_(4.03)O₁₂ 5.764 62 1119216.52 Bi_(1.4)Y_(.42)Ca_(1.18)In_(.4)V_(.59)Fe_(4.01)O₁₂ 5.754 53 1069214.41 Bi_(1.4)Y_(.38)Ca_(1.22)In_(.4)V_(.61)Fe_(3.99)O₁₂ 5.731 53 1041213.09 Bi_(1.4)Y_(.34)Ca_(1.26)In_(.4)V_(.63)Fe_(3.97)O₁₂ 5.709 47 1011211.3 Bi_(1.4)Gd_(.24)Ca_(1.36)Zr_(.36)V_(.50)Fe_(4.12)O_(11.97) 5.72539 1130 222.4 26.92Bi_(1.46)Gd_(.18)Ca_(1.36)Zr_(.36)V_(.50)Fe_(4.12)O_(11.97) 5.740 291179 221.5 27.57

FIG. 3 illustrates a generalized relationship between magnetization andtemperature. The figure shows the temperature where the magnetizationfalls to zero, known as the Curie temperature. When the magnetizationfalls to zero, the material can no longer be used as a magnetic materialfor radiofrequency activity. Accordingly, the Curie temperature dictatesthe maximum use temperature of the magnetic material, such as in anisolator or circulator. Thus, it can be advantageous to shift the Curietemperature to higher temperatures, thereby allowing for higheroperating temperatures. Further, when an increased number of components,such as isolators and circulators, are put close to one another, thiscan increase the heat. By having the improved Curie temperatures, moreisolators and circulators can be placed next to each other, therebyincreasing the capacity of operational efficiency.

As shown, many of the materials in Table 1 have high Curie temperatures.In some embodiments, the Curie temperature (in ° C.) can be above 200(or above about 200), above 210 (or above about 210), above 215 (orabove about 215), or above 220 (or above about 220). In someembodiments, the Curie temperatures can be below 230 (or below about230), below 225 (or below about 225), or below 220 (or below about 220).In some embodiments, the maximum operating temperature of the materialis at least 50° C. less (or at least about 50° C. less) than the Curietemperature of the material.

Improvements in the Curie temperature allow for the material to be usedin an increased temperature range as the Curie temperature isessentially the maximum temperature the material would work at. If amagnet is heated up enough, e.g., beyond the Curie temperature, it wouldlose its magnetization which would make the material non-usable for RFapplications. While the magnetization loss is not a step function (e.g.,it doesn't drop immediately to 0), magnetization does decrease after theCurie temperature, in some embodiments relatively quickly. Accordingly,the further away from the use temperature the Curie temperature is, thebetter temperature stability the material to have. Thus, it can beadvantageous to have a significant space between the operatingtemperature and the Curie temperature (such as at least about 50° C.).Further, it can be advantageous to avoid temperature fluctuations asthis would cause variations in resonant frequency.

The relationship between Curie temperature and device operatingtemperature below resonance can depend on the achievable bandwidth atthe operating temperature, which in turn can depends on themagnetization at that temperature. However, consideration can also begiven to the magnetization at the lowest frequency at the lowesttemperature. So the variation of the magnetization with temperature isthe real determinant, which to some extent depends on the Curietemperature's effect on the magnetization/temperature slope.

In some embodiments, the disclosed material (and thus the devicesutilizing the disclosed material) can be completely temperatureindependent from −20° C. to 100° C. (or between about −20° C. and about100° C.) (e.g., these temperatures are below the Curie temperature asthe magnetization starts to decrease well below the Curie temperature).In some embodiments, the disclosed material (and thus the devicesutilizing the disclosed material) can be completely temperatureindependent from −20° C. to 150° C. (or between about −20° C. and about150° C.) (e.g., these temperatures are below the Curie temperature asthe magnetization starts to decrease well below the Curie temperature).In some embodiments, the disclosed material (and thus the devicesutilizing the disclosed material) can be completely temperatureindependent from −20° C. to 200° C. (or between about −20° C. and about200° C.) (e.g., these temperatures are below the Curie temperature asthe magnetization starts to decrease well below the Curie temperature).

In some embodiments, the disclosed material (and thus the devicesutilizing the disclosed material) can be completely temperatureindependent from 0° C. to 100° C. (or between about 0° C. and about 100°C.) (e.g., these temperatures are below the Curie temperature as themagnetization starts to decrease well below the Curie temperature). Insome embodiments, the disclosed material (and thus the devices utilizingthe disclosed material) can be completely temperature independent from0° C. to 150° C. (or between about 0° C. and about 150° C.) (e.g., thesetemperatures are below the Curie temperature as the magnetization startsto decrease well below the Curie temperature). In some embodiments, thedisclosed material (and thus the devices utilizing the disclosedmaterial) can be completely temperature independent from 0° C. to 200°C. (or between about 0° C. and about 200° C.) (e.g., these temperaturesare below the Curie temperature as the magnetization starts to decreasewell below the Curie temperature).

In some embodiments, temperature independent can mean that the materialundergoes less than a 5 (or about 5) gauss change in magnetization per10° C. temperature change. In some embodiments, temperature independentcan mean that the material undergoes less than a 3 (or about 3) gausschange in magnetization per 10° C. temperature change. In someembodiments, temperature independent can mean that the materialundergoes less than a 1 (or about 1) gauss change in magnetization per10° C. temperature change. In some embodiments, temperature independentcan mean that the material undergoes less than a 0.5 (or about 0.5)gauss change in magnetization per 5° C. temperature change. In someembodiments, temperature independent can mean that the materialundergoes less than a 0.3 (or about 0.3) gauss change in magnetizationper 5° C. temperature change. In some embodiments, temperatureindependent can mean that the material undergoes less than a 0.1 (orabout 0.1) gauss change in magnetization per 5° C. temperature change.

As an example, for a 1.8 to 2.7 GHz device, an advantageous material canhave a room temperature 4PiMs of 700 Gauss, but a Curie temperature ofat least 180° C. using only a single transformer, which would give justthe right bandwidth at room temperature. However, there can be a balancebetween size and fragility of the transformer as too small of atransformer may be too weak to withstand application.

Above resonance can be more straightforward, the main consideration ismagnetization for bandwidth at the highest temperature. For mostapplications, the Curie temperature can exceed 200° C. at magnetizationsin the 1600-2000 Gauss region, with real linewidths less than 40 Oe. At1200 Gauss, Curie temperatures in the 180-200° C. range is likelyacceptable, but the linewidth may be minimized to below about 20 Oe.

In general, for above-resonance applications, any material can be usedat any frequency, however the main trade-off is the bandwidth v. thelevel of biasing field required for the given frequency. Highermagnetization will provide a broader bandwidth device but will alsorequire a higher level of biasing field. Higher biasing fields are alsorequired for higher operating frequencies, this is usually the limitingfactor to the magnetization level of the material used

In addition to the Curie temperatures discussed above, many of thematerials disclosed herein have high dielectric constants. For example,in some embodiments the material may have a dielectric constant above 20(or above about 20), above 21 (or above about 21), above 22 (or aboveabout 22), above 23 (or above about 23), above 24 (or above about 24),above 25 (or above about 25), above 26 (or above about 26), or above 27(or above about 27). In some embodiments, the material can have adielectric constant below 30 (or below about 30), below 27 (or belowabout 27), below 26 (or below about 26), or below 25 (or below about25). In some embodiments, the material can have a dielectric constant ofbetween 24 and 30 (or between about 24 and about 30). In someembodiments, the material can have a dielectric constant of between 24and 28 (or between about 24 and about 28).

In some embodiments, it can be advantageous to keep the material with a3 dB linewidth of below a certain level, e.g., minimizing the linewidth.In some embodiments, the 3 dB linewidth can be below 100 (or below about100), below 80 (or below about 80), below 60 (or below about 60), orbelow 50 (or below about 50). In some embodiments, the 3 dB linewidthcan be above 40 (or above about 40), above 50 (or above about 50), orabout 60 (or above about 60).

In some embodiments, the material can have high magnetization. In someembodiments, the magnetization range can be between 400 and 1600 gauss(or about 400 and about 1600 gauss). In some embodiments, themagnetization range can be between 800 and 1400 gauss (or between about800 and about 1400 gauss). In some embodiments, the material can have amagnetization of above 1000 (or above about 1000), above 1100 (or aboveabout 1100), or above 1200 (or above about 1200) gauss. In someembodiments, the magnetization can be below 1200 (or below about 1200),below 1100 (or below about 1100), or below 1000 (or below about 1000)gauss.

Preparation of the Modified Synthetic Garnet Compositions:

The preparation of the modified synthetic garnet materials can beaccomplished by using known ceramic techniques. A particular example ofthe process flow is illustrated in FIG. 4.

As shown in FIG. 4, the process begins with step 106 for weighing theraw material. The raw material may include oxides and carbonates such asIron Oxide (Fe₂O₃), Bismuth Oxide (Bi₂O₃), Yttrium Oxide (Y₂O₃), CalciumCarbonate (CaCO₃), Zirconium Oxide (ZrO₂), Gadolinium Oxide (Gd₂O₃),Vanadium Pentoxide (V₂₀₅), Yttrium Vanadate (YVO₄), Bismuth Niobate(BiNbO₄), Silica (SiO₂), Niobium Pentoxide (Nb₂O₅), Antimony Oxide(Sb₂O₃), Molybdenum Oxide (MoO₃), Indium Oxide (In₂O₃), or combinationsthereof. In one embodiment, raw material consisting essentially of about35-40 wt % Bismuth Oxide, more preferably about 38.61 wt %; about 10-12wt % Calcium Oxide, more preferably about 10.62 wt %; about 35-40 wt %Iron Oxide, more preferably about 37 wt %, about 5-10 wt % ZirconiumOxide, more preferably about 8.02 wt %; about 4-6 wt % Vanadium Oxide,more preferably about 5.65 wt %. In addition, organic based materialsmay be used in a sol gel process for ethoxides and/or acrylates orcitrate based techniques may be employed. Other known methods in the artsuch as co-precipitation of hydroxides, sol-gel, or laser ablation mayalso be employed as a method to obtain the materials. The amount andselection of raw material depend on the specific formulation.

After the raw materials are weighed, they are blended in Step 108 usingmethods consistent with the current state of the ceramic art, which caninclude aqueous blending using a mixing propeller, or aqueous blendingusing a vibratory mill with steel or zirconia media. In someembodiments, a glycine nitrate or spray pyrolysis technique may be usedfor blending and simultaneously reacting the raw materials.

The blended oxide is subsequently dried in Step 110, which can beaccomplished by pouring the slurry into a pane and drying in an oven,preferably between 100-400° C. or by spray drying, or by othertechniques known in the art.

The dried oxide blend is processed through a sieve in Step 112, whichhomogenizes the powder and breaks up soft agglomerates that may lead todense particles after calcining.

The material is subsequently processed through a pre-sintering calciningin Step 114. Preferably, the material is loaded into a container such asan alumina or cordierite sagger and heat treated in the range of about800-1000° C. In some embodiments, a heat treatment in the range of about500-1000° C. can be used. In some embodiments, a heat treatment in therange of about 900-950° C. can be used. In some embodiments, a heattreatment in the range of about 500-700° C. can be used. Preferably, thefiring temperature is low as higher firing temperatures have an adverseeffect on linewidth.

After calcining, the material is milled in Step 116, preferably in avibratory mill, an attrition mill, a jet mill or other standardcomminution technique to reduce the median particle size into the rangeof about 0.01 to 0.1 microns, though in some embodiments larger sizessuch as 0.5 micron to 10 microns can be used as well. Milling ispreferably done in a water based slurry but may also be done in ethylalcohol or another organic based solvent.

The material is subsequently spray dried in Step 118. During the spraydrying process, organic additives such as binders and plasticizers canbe added to the slurry using techniques known in the art. The materialis spray dried to provide granules amenable to pressing, preferably inthe range of about 10 microns to 150 microns in size.

The spray dried granules are subsequently pressed in Step 120,preferably by uniaxial or isostatic pressing to achieve a presseddensity to as close to 60% of the x-ray theoretical density as possible.In addition, other known methods such as tape casting, tape calendaringor extrusion may be employed as well to form the unfired body.

The pressed material is subsequently processed through a calciningprocess in Step 122. Preferably, the pressed material is placed on asetter plate made of material such as alumina which does not readilyreact with the garnet material. The setter plate is heated in a periodickiln or a tunnel kiln in air or pressure oxygen in the range of betweenabout 850° C.-1000° C. to obtain a dense ceramic compact. In someembodiments, a heat treatment in the range of about 500-1000° C. can beused. In some embodiments, a heat treatment in the range of about500-700° C. can be used. Other known treatment techniques, such asinduction heat, hot pressing, fast firing, or assisted fast firing, mayalso be used in this step. In some embodiments, a density having >98% ofthe theoretical density can be achieved.

The dense ceramic compact is machined in the Step 124 to achievedimensions suitable or the particular applications.

Devices Incorporating Ultra High Dielectric Constant Garnet

Radio-frequency (RF) applications that utilize synthetic garnetcompositions, such as those disclosed above, can include ferrite deviceshaving relatively low magnetic resonance linewidths. RF applications canalso include devices, methods, and/or systems having or related togarnet compositions having reduced or substantially nil reduced earthcontent. As described herein, such garnet compositions can be configuredto yield relatively high dielectric constants; and such a feature can beutilized to provide advantageous functionalities. It will be understoodthat at least some of the compositions, devices, and methods describedin reference above can be applied to such implementations.

FIG. 5 shows a radio-frequency (RF) device 200 having garnet structureand chemistry such as disclosed herein, and thus a plurality ofdodecahedral structures, octahedral structures, and tetrahedralstructures. The device 200 can include garnet structures (e.g., a garnetstructure 220) formed from such dodecahedral, octahedral, andtetrahedral structures. Disclosed herein are various examples of howdodecahedral sites 212, octahedral sites 208, and tetrahedral sites 204can be filled by or substituted with different ions to yield one or moredesirable properties for the RF device 200. Such properties can include,but are not limited to desirable RF properties and cost-effectiveness ofmanufacturing of ceramic materials that can be utilized to fabricate theRF device 200. By way of an example, disclosed herein are ceramicmaterials having relatively high dielectric constants, and havingreduced or substantially nil rare earth contents.

Some design considerations for achieving such features are nowdescribed. Also described are example devices and related RF performancecomparisons. Also described are example applications of such devices, aswell as fabrication examples.

Bismuth Garnets:

Single crystal materials with a formulaBi_((3−2x))Ca_(2x)Fe_(5−x)V_(x)O₁₂ have been grown in the past, where xwas 1.25. A 4 πM_(s) value of about 600 Gauss was obtained (which issuitable for some tunable filters and resonators in a 1-2 GHz range),with linewidths of about 1 Oersted, indicating low intrinsic magneticlosses for the system. However, the level of Bi substitution was onlyabout 0.5 in the formula.

Attempts to make single phase polycrystalline materials (with a formulaBi_(3−2x)Ca_(2x)V_(x)Fe_(5−x)O₁₂) similar to the single crystalmaterials were successful only in a region of x>0.96, effectivelyconfining the 4πM_(s) to less than about 700 Oersted and resulting inpoor linewidths (greater than 100 Oersted). Small amounts of Al⁺³reduced the linewidth to about 75 Oersted, but increased Al⁺³ reduced4πM_(s). Bi substitution was only about 0.4 in the formula for thesematerials.

For Faraday rotation devices, the Faraday rotation can be essentiallyproportionate to the level of Bi substitution in garnets, raisinginterest in increasing the level of substitution. Anisotropy isgenerally not a major factor for optical applications, so substitutionon the octahedral and tetrahedral site can be based on maximizing therotation. Thus, in such applications, it may be desirable to introduceas much Bi⁺³ into the dodecahedral site as possible. The maximum levelof Bi⁺³ can be influenced by the size of the dodecahedral rare earthtrivalent ion.

In some situations, the level of Bi⁺³ substitution can be affected bysubstitutions on the other sites. Because Bi⁺³ is non-magnetic, it caninfluence the Faraday rotation through its effect on the tetrahedral andoctahedral Fe⁺³ ions. Since this is thought to be a spin-orbitalinteraction, where Bi⁺³ modifies existing Fe⁺³ pair transitions, one canexpect both a change in the anisotropy of the Fe⁺³ ions and opticaleffects including large Faraday rotation. The Curie temperature of Bi⁺³substituted YIG can also increase at low Bi⁺³ substitution.

Examples of Devices Having Rare Earth Free or Reduced Garnets:

As described herein, garnets having reduced or no rare earth content canbe formed, and such garnets can have desirable properties for use indevices for applications such as RF applications. In someimplementations, such devices can be configured to take advantage ofunique properties of the Bi⁺³ ion. For example, the “lone pair” ofelectrons on the Bi⁺³ ion can raise the ionic polarizability and hencethe dielectric constant.

Further, because the center frequency of a ferrite device (such as agarnet disk) operating in a split polarization transverse magnetic (TM)mode is proportional to 1/(ε)^(1/2), doubling the dielectric constant(e) can reduce the frequency by a factor of square root of 2(approximately 1.414). As described herein in greater detail, increasingthe dielectric constant by, for example, a factor of 2, can result in areduction in a lateral dimension (e.g., diameter) of a ferrite disk byfactor of square root of 2. Accordingly, the ferrite disk's area can bereduced by a factor of 2. Such a reduction in size can be advantageoussince the device's footprint area on an RF circuit board can be reduced(e.g., by a factor of 2 when the dielectric constant is increased by afactor of 2). Although described in the context of the example increaseby a factor of 2, similar advantages can be realized in configurationsinvolving factors that are more or less than 2.

Reduced Size Circulators/Isolators Having Ferrite with High DielectricConstant

As described herein, ferrite devices having garnets with reduced or norare earth content can be configured to include a high dielectricconstant property. Various design considerations concerning dielectricconstants as applied to RF applications are now described. In someimplementations, such designs utilizing garnets with high dielectricconstants may or may not necessarily involve rare earth freeconfigurations.

Values of dielectric constant for microwave ferrite garnets and spinelscommonly fall in a range of 12 to 18 for dense polycrystalline ceramicmaterials. Such garnets are typically used for above ferromagneticresonance applications in, for example, UHF and low microwave region,because of their low resonance linewidth. Such spinels are typicallyused at, for example, medium to high microwave frequencies, for belowresonance applications, because of their higher magnetization. Most, ifnot substantially all, circulators or isolators that use such ferritedevices are designed with triplate/stripline or waveguide structures.

Dielectric constant values for low linewidth garnets is typically in arange of 14 to 16. These materials can be based on Yttrium iron garnet(YIG) with a value of approximately 16, or substituted versions of thatchemistry with Aluminum or, for example, Zirconium/Vanadium combinationswhich can reduce the value to around 14. Although for example LithiumTitanium based spinel ferrites exist with dielectric constants up toclose to 20, these generally do not have narrow linewidths; and thus arenot suitable for many RF applications. However, as described in detailabove, garnets made using Bismuth substituted for Yttrium can have muchhigher dielectric constants.

In some embodiments, an increase in dielectric constant can bemaintained for compositions containing Bismuth, including those withother non-magnetic substitution on either or both of the octahedral andtetrahedral sites (e.g., Zirconium or Vanadium, respectively). By usingions of higher polarization, it is possible to further increase thedielectric constant. For example, Niobium or Titanium can be substitutedinto the octahedral or tetrahedral site; and Titanium can potentiallyenter both sites.

In some embodiments, a relationship between ferrite device size,dielectric constant, and operating frequency can be represented asfollows. There are different equations that can characterize differenttransmission line representations. For example, in above-resonancestripline configurations, the radius R of a ferrite disk can becharacterized asR=1.84/[2π(effective permeability)×(dielectric constant)]^(1/2)  (1)where (effective permeability)=H_(dc)+4πM_(s)/H_(dc), with H_(dc) beingthe magnetic field bias. Equation 1 shows that, for a fixed frequencyand magnetic bias, the radius R is inversely proportional to the squareroot of the dielectric constant.

In another example, in below-resonance stripline configurations, arelationship for ferrite disk radius R similar to Equation 1 can beutilized for weakly coupled quarter wave circulators where the low biasfield corresponds to below-resonance operation. For below-resonancewaveguide configurations (e.g., in disk or rod waveguides), both lateraldimension (e.g., radius R) and thickness d of the ferrite can influencethe frequency. However, the radius R can still be expressed asR=λ/[2π(dielectric constant)^(1/2)][((πR)/(2d))²⁺(1.84)²]^(1/2)  (2)which is similar to Equation 1 in terms of relationship between R anddielectric constant.

The example relationship of Equation 2 is in the context of a circulardisk shaped ferrites. For a triangular shaped resonator, the samewaveguide expression can used, but in this case, A (altitude of thetriangle) being equal to 3.63×λ/2π applies instead of the radius in thecircular disk case.

In all of the foregoing example cases, one can see that by increasingthe dielectric constant (e.g., by a factor of 2), one can expect toreduce the size of the ferrite (e.g., circular disk or triangle) by afactor of square root of 2, and thereby reduce the area of the ferriteby a factor of 2. As described in reference to Equation 2, thickness ofthe ferrite can also be reduced.

In implementations where ferrite devices are used as RF devices, sizesof such RF devices can also be reduced. For example, in a striplinedevice, a footprint area of the device can be dominated by the area ofthe ferrite being used. Thus, one can expect that a correspondingreduction in device size would be achieved. In a waveguide device, adiameter of the ferrite being used can be a limiting factor indetermining size. However, a reduction provided for the ferrite diametermay be offset by the need to retain wavelength-related dimensions in themetal part of the junction.

Examples of Reduced-Size Ferrite

As described herein, ferrite size can be reduced significantly byincreasing the dielectric constant associated with garnet structures.Also as described herein, garnets with reduced Yttrium and/or reducednon-Y rare earth content can be formed by appropriate Bismuthsubstitutions. In some embodiments, such garnets can includeYttrium-free or rare earth free garnets. An example RF device havingferrite devices with increased dielectric constant and Yttrium-freegarnets is described in reference to FIGS. 6-7.

FIGS. 6A and 6B summarize the example ferrite size reductions describedherein. As described herein and shown in FIG. 6A, a ferrite device 250can be a circular-shaped disk having a reduced diameter of 2R′ and athickness of d′. The thickness may or may not be reduced. As describedin reference to Equation 1, the radius R of a circular-shaped ferritedisk can be inversely proportional to the square root of the ferrite'sdielectric constant. Thus, the increased dielectric constant of theferrite device 250 is shown to yield its reduced diameter 2 W.

As described herein and shown in FIG. 6B, a ferrite device 250 can alsobe a triangular-shaped disk having a reduced side dimension of S′ and athickness of d′. The thickness may or may not be reduced. As describedin reference to Equation 2, the altitude A of a triangular-shapedferrite disk (which can be derived from the side dimension S) can beinversely proportional to the square root of the ferrite's dielectricconstant. Thus, the increased dielectric constant of the ferrite device250 is shown to yield its reduced dimension S′.

Although described in the context of example circular and triangleshaped ferrites, one or more features of the present disclosure can alsobe implemented in other shaped ferrites.

FIGS. 7A and 7B show an example of a circulator 300 having a pair offerrite disks 302, 312 disposed between a pair of cylindrical magnets306, 316. Each of the ferrite disks 302, 312 can be a ferrite diskhaving one or more features described herein. FIG. 7A shows anun-assembled view of a portion of the example circulator 300. FIG. 7Bshows a side view of the example circulator 300.

In the example shown, the first ferrite disk 302 is shown to be mountedto an underside of a first ground plane 304. An upper side of the firstground plane 304 is shown to define a recess dimensioned to receive andhold the first magnet 306. Similarly, the second ferrite disk 312 isshown to be mounted to an upper side of a second ground plane 314; andan underside of the second ground plane 314 is shown to define a recessdimensioned to receive and hold the second magnet 316.

The magnets 306, 316 arranged in the foregoing manner can yieldgenerally axial field lines through the ferrite disks 302, 312. Themagnetic field flux that passes through the ferrite disks 302, 312 cancomplete its circuit through return paths provided by 320, 318, 308 and310 so as to strengthen the field applied to the ferrite disks 302, 312.In some embodiments, the return path portions 320 and 310 can be diskshaving a diameter larger than that of the magnets 316, 306; and thereturn path portions 318 and 308 can be hollow cylinders having an innerdiameter that generally matches the diameter of the return path disks320, 310. The foregoing parts of the return path can be formed as asingle piece or be an assembly of a plurality of pieces.

The example circulator device 300 can further include an inner fluxconductor (also referred to herein as a center conductor) 322 disposedbetween the two ferrite disks 302, 312. Such an inner conductor can beconfigured to function as a resonator and matching networks to the ports(not shown).

Various examples of new garnet systems and devices related thereto aredescribed herein. In some embodiments, such garnet systems can containhigh levels of Bismuth, which can allow formation of low loss ferritedevices. Further, by selected addition of other elements, one can reduceor eliminate rare earth content of garnets, including commercialgarnets. Reduction or elimination of such rare earth content caninclude, but is not limited to, Yttrium. In some embodiments, the garnetsystems described herein can be configured to significantly increase(e.g., double) the dielectric constant of non-Bi garnets, therebyoffering the possibility of significantly decreasing (e.g., halving) theprinted circuit “footprint” of ferrite devices associated withconventional garnets.

In some embodiments, ferrite-based circulator devices having one or morefeatures as described herein can be implemented as a packaged modulardevice. FIG. 8 shows an example packaged device 400 having a circulatordevice 300 (for example as shown in FIG. 7B) mounted on a packagingplatform 404 and enclosed by a housing structure 402. The exampleplatform 404 is depicted as including a plurality of holes 408dimensioned to allow mounting of the packaged device 400. The examplepackaged device 400 is shown further include example terminals 406 a-406c configured to facilitate electrical connections.

In some embodiments, a packaged circulator/isolator 3002 such as theexample of FIG. 8 can be implemented in a circuit board or module 3004as shown in FIG. 18. Such a circuit board can include a plurality ofcircuits configured to perform one or more radio-frequency (RF) relatedoperations. The circuit board can also include a number of connectionfeatures configured to allow transfer of RF signals and power betweenthe circuit board and components external to the circuit board.

In some embodiments, the foregoing example circuit board can include RFcircuits associated with a front-end module of an RF apparatus. As shownin FIG. 9, such an RF apparatus can include an antenna 5012 that isconfigured to facilitate transmission and/or reception of RF signals.Such signals can be generated by and/or processed by a transceiver 5014.For transmission, the transceiver 5014 can generate a transmit signalthat is amplified by a power amplifier (PA) and filtered (Tx Filter) fortransmission by the antenna 5012. For reception, a signal received fromthe antenna 5012 can be filtered (Rx Filter) and amplified by alow-noise amplifier (LNA) before being passed on to the transceiver5014. In the example context of such Tx and Rx paths, circulators and/orisolators 5000 having one or more features as described herein can beimplemented at or in connection with, for example, the PA circuit andthe LNA circuit.

In some embodiments, circuits and devices having one or more features asdescribed herein can be implemented in RF applications such as awireless base-station. Such a wireless base-station can include one ormore antennas 5012, such as the example described in reference to FIG.9, configured to facilitate transmission and/or reception of RF signals.Such antenna(s) can be coupled to circuits and devices having one ormore circulators/isolators as described herein.

As described herein, terms “circulator” and “isolator” can be usedinterchangeably or separately, depending on applications as generallyunderstood. For example, circulators can be passive devices utilized inRF applications to selectively route RF signals between an antenna, atransmitter, and a receiver. If a signal is being routed between thetransmitter and the antenna, the receiver preferably should be isolated.Accordingly, such a circulator is sometimes also referred to as anisolator; and such an isolating performance can represent theperformance of the circulator.

Fabrication of RF Devices

FIGS. 10-14 show examples of how ferrite devices having one or morefeatures as described herein can be fabricated. FIG. 10 shows a process20 that can be implemented to fabricate a ceramic material having one ormore of the foregoing properties. In block 21, powder can be prepared.In block 22, a shaped object can be formed from the prepared powder. Inblock 23, the formed object can be sintered. In block 24, the sinteredobject can be finished to yield a finished ceramic object having one ormore desirable properties.

In implementations where the finished ceramic object is part of adevice, the device can be assembled in block 25. In implementationswhere the device or the finished ceramic object is part of a product,the product can be assembled in block 26.

FIG. 10 further shows that some or all of the steps of the exampleprocess 20 can be based on a design, specification, etc. Similarly, someor all of the steps can include or be subjected to testing, qualitycontrol, etc.

In some implementations, the powder preparation step (block 21) of FIG.10 can be performed by the example process described in reference toFIG. 14. Powder prepared in such a manner can include one or moreproperties as described herein, and/or facilitate formation of ceramicobjects having one or more properties as described herein.

In some implementations, powder prepared as described herein can beformed into different shapes by different forming techniques. By way ofexamples, FIG. 11 shows a process 50 that can be implemented topress-form a shaped object from a powder material prepared as describedherein. In block 52, a shaped die can be filled with a desired amount ofthe powder. In FIG. 12, configuration 60 shows the shaped die as 61 thatdefines a volume 62 dimensioned to receive the powder 63 and allow suchpower to be pressed. In block 53, the powder in the die can becompressed to form a shaped object. Configuration 64 shows the powder inan intermediate compacted form 67 as a piston 65 is pressed (arrow 66)into the volume 62 defined by the die 61. In block 54, pressure can beremoved from the die. In block 55, the piston (65) can be removed fromthe die (61) so as to open the volume (62). Configuration 68 shows theopened volume (62) of the die (61) thereby allowing the formed object 69to be removed from the die. In block 56, the formed object (69) can beremoved from the die (61). In block 57, the formed object can be storedfor further processing.

In some implementations, formed objects fabricated as described hereincan be sintered to yield desirable physical properties as ceramicdevices. FIG. 13 shows a process 70 that can be implemented to sintersuch formed objects. In block 71, formed objects can be provided. Inblock 72, the formed objects can be introduced into a kiln. In FIG. 14,a plurality of formed objects 69 are shown to be loaded into a sinteringtray 80. The example tray 80 is shown to define a recess 83 dimensionedto hold the formed objects 69 on a surface 82 so that the upper edge ofthe tray is higher than the upper portions of the formed objects 69.Such a configuration allows the loaded trays to be stacked during thesintering process. The example tray 80 is further shown to definecutouts 83 at the side walls to allow improved circulation of hot gas atwithin the recess 83, even when the trays are stacked together. FIG. 14further shows a stack 84 of a plurality of loaded trays 80. A top cover85 can be provided so that the objects loaded in the top tray generallyexperience similar sintering condition as those in lower trays.

In block 73, heat can be applied to the formed objects so as to yieldsintered objects. Such application of heat can be achieved by use of akiln. In block 74, the sintered objects can be removed from the kiln. InFIG. 14, the stack 84 having a plurality of loaded trays is depicted asbeing introduced into a kiln 87 (stage 86 a). Such a stack can be movedthrough the kiln (stages 86 b, 86 c) based on a desired time andtemperature profile. In stage 86 d, the stack 84 is depicted as beingremoved from the kiln so as to be cooled.

In block 75, the sintered objects can be cooled. Such cooling can bebased on a desired time and temperature profile. In block 206, thecooled objects can undergo one or more finishing operations. In block207, one or more tests can be performed.

Heat treatment of various forms of powder and various forms of shapedobjects are described herein as calcining, firing, annealing, and/orsintering. It will be understood that such terms may be usedinterchangeably in some appropriate situations, in context-specificmanners, or some combination thereof.

Telecommunication Base Station

Circuits and devices having one or more features as described herein canbe implemented in RF applications such as a wireless base-station. Sucha wireless base-station can include one or more antennas configured tofacilitate transmission and/or reception of RF signals. Such antenna(s)can be coupled to circuits and devices having one or morecirculators/isolators as described herein.

Thus, in some embodiments, the above disclosed material can beincorporated into different components of a telecommunication basestation, such as used for cellular networks and wireless communications.An example perspective view of a base station 2000 is shown in FIG. 15,including both a cell tower 2002 and electronics building 2004. The celltower 2002 can include a number of antennas 2006, typically facingdifferent directions for optimizing service, which can be used to bothreceive and transmit cellular signals while the electronics building2004 can hold electronic components such as filters, amplifiers, etc.discussed below. Both the antennas 2006 and electronic components canincorporate embodiments of the disclosed ceramic materials.

FIG. 12 shows a schematic view of a base station such as shown in FIG.15. As shown, the base station can include an antenna 412 that isconfigured to facilitate transmission and/or reception of RF signals.Such signals can be generated by and/or processed by a transceiver 414.For transmission, the transceiver 414 can generate a transmit signalthat is amplified by a power amplifier (PA) and filtered (Tx Filter) fortransmission by the antenna 412. For reception, a signal received fromthe antenna 412 can be filtered (Rx Filter) and amplified by a low-noiseamplifier (LNA) before being passed on to the transceiver 414. In theexample context of such Tx and Rx paths, circulators and/or isolators400 having one or more features as described herein can be implementedat or in connection with, for example, the PA circuit and the LNAcircuit. The circulators and isolators can include embodiments of thematerial disclosed herein. Further, the antennas can include thematerials disclosed herein, allowing them to work on higher frequencyranges.

FIG. 16 illustrates hardware 2010 that can be used in the electronicsbuilding 2004, and can include the components discussed above withrespect to FIG. 12. For example, the hardware 2010 can be a base stationsubsystem (BSS), which can handle traffic and signaling for the mobilesystems.

FIG. 17 illustrates a further detailing of the hardware 2010 discussedabove. Specifically, FIG. 17 depicts a cavity filter/combiner 2020 whichcan be incorporated into the base station. The cavity filter 2020 caninclude, for example, bandpass filters such as those incorporatingembodiments of the disclosed material, and can allow the output of twoor more transmitters on different frequencies to be combined.

Additionally, embodiments of the disclosure can be general temperatureinsensitive at operation temperatures (temperature insensitive isolatorsand circulators) due to the high Curie temperatures discussed above.Accordingly, embodiments of the disclosure can be high temperatureisolators and circulators, which can be used in high temperature basestations such as those discussed herein.

From the foregoing description, it will be appreciated that an inventivegarnets and method of manufacturing are disclosed. While severalcomponents, techniques and aspects have been described with a certaindegree of particularity, it is manifest that many changes can be made inthe specific designs, constructions and methodology herein abovedescribed without departing from the spirit and scope of thisdisclosure.

Certain features that are described in this disclosure in the context ofseparate implementations can also be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation can also be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations, one or more features from a claimed combination can, insome cases, be excised from the combination, and the combination may beclaimed as any subcombination or variation of any subcombination.

Moreover, while methods may be depicted in the drawings or described inthe specification in a particular order, such methods need not beperformed in the particular order shown or in sequential order, and thatall methods need not be performed, to achieve desirable results. Othermethods that are not depicted or described can be incorporated in theexample methods and processes. For example, one or more additionalmethods can be performed before, after, simultaneously, or between anyof the described methods. Further, the methods may be rearranged orreordered in other implementations. Also, the separation of varioussystem components in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described components and systems cangenerally be integrated together in a single product or packaged intomultiple products. Additionally, other implementations are within thescope of this disclosure.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include or do not include, certain features, elements,and/or steps. Thus, such conditional language is not generally intendedto imply that features, elements, and/or steps are in any way requiredfor one or more embodiments.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than or equal to 10% of, within less than or equal to 5% of, withinless than or equal to 1% of, within less than or equal to 0.1% of, andwithin less than or equal to 0.01% of the stated amount. If the statedamount is 0 (e.g., none, having no), the above recited ranges can bespecific ranges, and not within a particular % of the value. Forexample, within less than or equal to 10 wt./vol. % of, within less thanor equal to 5 wt./vol. % of, within less than or equal to 1 wt./vol. %of, within less than or equal to 0.1 wt./vol. % of, and within less thanor equal to 0.01 wt./vol. % of the stated amount.

Some embodiments have been described in connection with the accompanyingdrawings. The figures are drawn to scale, but such scale should not belimiting, since dimensions and proportions other than what are shown arecontemplated and are within the scope of the disclosed inventions.Distances, angles, etc. are merely illustrative and do not necessarilybear an exact relationship to actual dimensions and layout of thedevices illustrated. Components can be added, removed, and/orrearranged. Further, the disclosure herein of any particular feature,aspect, method, property, characteristic, quality, attribute, element,or the like in connection with various embodiments can be used in allother embodiments set forth herein. Additionally, it will be recognizedthat any methods described herein may be practiced using any devicesuitable for performing the recited steps.

While a number of embodiments and variations thereof have been describedin detail, other modifications and methods of using the same will beapparent to those of skill in the art. Accordingly, it should beunderstood that various applications, modifications, materials, andsubstitutions can be made of equivalents without departing from theunique and inventive disclosure herein or the scope of the claims.

What is claimed is:
 1. A ceramic material having a compositionincluding: Bi_(1.4)Y_(0.66)Ca_(0.94)In_(0.4)V_(0.47)Fe_(4.13)O₁₂;Bi_(1.4)Y_(0.62)Ca_(0.98)In_(0.4)V_(0.49)Fe_(4.11)O₁₂;Bi_(1.4)Y_(0.58)Ca_(1.02)In_(0.4)V_(0.51)Fe_(4.09)O₁₂;Bi_(1.4)Y_(0.54)Ca_(1.06)In_(0.4)V_(0.53)Fe_(4.07)O₁₂;Bi_(1.4)Y_(0.50)Ca_(1.11)In_(0.4)V_(0.55)Fe_(4.05)O₁₂;Bi_(1.4)Y_(0.46)Ca_(1.14)In_(0.4)V_(0.57)Fe_(4.03)O₁₂;Bi_(1.4)Y_(0.42)Ca_(1.18)In_(0.4)V_(0.59)Fe_(4.01)O₁₂;Bi_(1.4)Y_(0.38)Ca_(1.221)n_(0.4)V_(0.61)Fe_(3.99)O₁₂;Bi_(1.4)Y_(0.34)Ca_(1.261)n_(0.4)V_(0.63)Fe_(3.97)O₁₂;Bi_(1.4)Gd_(0.24)Ca_(1.36)Zr_(0.36)V_(0.50)Fe_(4.12)O_(11.97); orBi_(1.46)Gd_(0.18)Ca_(1.36)Zr_(0.36)V_(0.50)Fe_(4.12)O_(11.97).
 2. Theceramic material of claim 1 wherein the composition has a dielectricconstant of at least
 25. 3. The ceramic material of claim 1 wherein theceramic material does not include aluminum.
 4. The ceramic material ofclaim 1 wherein the ceramic material has a Curie temperature of at least215.
 5. The ceramic material of claim 1 wherein the ceramic material hasa Curie temperature of at least
 220. 6. The ceramic material of claim 1wherein the ceramic material has a magnetization of at least
 1100. 7.The ceramic material of claim 1 wherein the ceramic material has amagnetization of at least
 1200. 8. An isolator including the ceramicmaterial of claim
 1. 9. The ceramic material of claim 1 wherein theceramic material has a Curie temperature of at least 215 and amagnetization of at least
 1100. 10. The ceramic material of claim 1wherein the ceramic material has a dielectric constant of above
 26. 11.A method of forming a synthetic garnet having temperature insensitivity,the method comprising: incorporating bismuth, calcium, indium, andvanadium into a crystal structure of an iron garnet structure to achievea composition including:Bi_(1.4)Y_(0.66)Ca_(0.94)In_(0.4)V_(0.47)Fe_(4.13)O₁₂;Bi_(1.4)Y_(0.62)Ca_(0.98)In_(0.4)V_(0.49)Fe_(4.11)O₁₂;Bi_(1.4)Y_(0.58)Ca_(1.02)In_(0.4)V_(0.51)Fe_(4.09)O₁₂;Bi_(1.4)Y_(0.54)Ca_(1.06)In_(0.4)V_(0.53)Fe_(4.07)O₁₂;Bi_(1.4)Y_(0.50)Ca_(1.11)In_(0.4)V_(0.55)Fe_(4.05)O₁₂;Bi_(1.4)Y_(0.46)Ca_(1.14)In_(0.4)V_(0.57)Fe_(4.03)O₁₂;Bi_(1.4)Y_(0.42)Ca_(1.18)In_(0.4)V_(0.59)Fe_(4.01)O₁₂;Bi_(1.4)Y_(0.38)Ca_(1.22)In_(0.4)V_(0.61)Fe_(3.99)O₁₂;Bi_(1.4)Y_(0.34)Ca_(1.26)In_(0.4)V_(0.63)Fe_(3.97)O₁₂;Bi_(1.4)Gd_(0.24)Ca_(1.36)Zr_(0.36)V_(0.50)Fe_(4.12)O_(11.97); orBi_(1.46)Gd_(0.18)Ca_(1.36)Zr_(0.36)V_(0.50)Fe_(4.12)O_(11.97).
 12. Themethod of claim 11 wherein the synthetic garnet does not includealuminum.
 13. The method of claim 11 wherein the synthetic garnet has aCurie temperature of at least
 215. 14. The method of claim 11 whereinthe synthetic garnet has a Curie temperature of at least
 220. 15. Themethod of claim 11 wherein the synthetic garnet has a magnetization ofat least
 1100. 16. The method of claim 11 wherein the synthetic garnethas a magnetization of at least
 1200. 17. The method of claim 11 furtherincluding forming an isolator including the synthetic garnet.
 18. Aceramic material having a composition including:Bi_(1.4)Y_(0.66)Ca_(0.94)In_(0.4)V_(0.47)Fe_(4.13)O₁₂;Bi_(1.4)Y_(0.62)Ca_(0.98)In_(0.4)V_(0.49)Fe_(4.11)O₁₂;Bi_(1.4)Y_(0.58)Ca_(1.02)In_(0.4)V_(0.51)Fe_(4.09)O₁₂;Bi_(1.4)Y_(0.54)Ca_(1.06)In_(0.4)V_(0.53)Fe_(4.07)O₁₂;Bi_(1.4)Y_(0.50)Ca_(1.11)In_(0.4)V_(0.55)Fe_(4.05)O₁₂;Bi_(1.4)Y_(0.46)Ca_(1.14)In_(0.4)V_(0.57)Fe_(4.03)O₁₂;Bi_(1.4)Gd_(0.24)Ca_(1.36)Zr_(0.36)V_(0.050)Fe_(4.12)O_(11.97); orBi_(1.46)Gd_(0.18)Ca_(1.36)Zr_(0.36)V_(0.50)Fe_(4.12)O_(11.97).
 19. Theceramic material of claim 18 wherein the ceramic material has a Curietemperature of at least 220 and the composition includes:Bi_(1.4)Y_(0.66)Ca_(0.94)In_(0.4)V_(0.47)Fe_(4.13)O₁₂;Bi_(1.4)Gd_(0.24)Ca_(1.36)Zr_(0.36)V_(0.50)Fe_(4.12)O_(11.97); orBi_(1.46)Gd_(0.18)Ca_(1.36)Zr_(0.36)V_(0.50)Fe_(4.12)O_(11.97).
 20. Theceramic material of claim 18 wherein the ceramic material has amagnetization of at least 1200 and the composition includes:Bi_(1.4)Y_(0.66)Ca_(0.94)In_(0.4)V_(0.47)Fe_(4.13)O₁₂;Bi_(1.4)Y_(0.62)Ca_(0.98)In_(0.4)V_(0.49)Fe_(4.11)O₁₂; orBi_(1.4)Y_(0.58)Ca_(1.02)In_(0.4)V_(0.51)Fe_(4.09)O₁₂.